The long term goal of the present study is to gain further insight into the observation that anti-immunoglobulin (anti-Ig) inhibits mitogen induced proliferation of certain human malignant B cell clones. An in vitro proliferative assay will be developed to characterize the effects of anti-Ig on human B cell malignancies. This assay will be used to identify clonal models for anti-Ig induced inhibition of malignant cell growth. These clonal models will be used to analyze the intracellular signals and biochemical events associated with the inhibitory effect of anti-Ig. These goals will be accomplished as follows. 1). Factors that may influence mitogen induced proliferation, and the ability of anti-Ig to inhibit mitogen induced proliferation, of human malignant lymphocytes will be evaluated. The need for T lymphocytes and monocytes, and serum factors, will be addressed. The nature of the anti-Ig-sIg interaction will be probed by comparing different anti-Ig reagents of different specificities. 2). Malignant lymphocytes from additional patients will be characterized, and the frequency of defined functional types among various morphological and phenotypic subsets of B lymphocyte malignancies will be determined. The assumption that information provided by in vitro assay cannot be duplicated by analysis of morphology or cell surface phenotype will be tested. 3). Human malignant B cell clones will be characterized with respect to actin binding proteins, actin, and calmodulin binding proteins. Comparisons will be made between human malignant B cell clones that respond to anti-Ig and cytochalasin in different ways. Static differences, and dynamic changes, in actin binding proteins and calmodulin binding proteins will be studied by polyacrylamide gel electrophoresis, supported in some cases by column chromatography. New protein synthesis and protein phosphorylation will be determined. The state of actin in the cell will be studied by inhibition of DNAase. Further understanding of the mechanisms by which anti-Ig inhibits human malignant B cell proliferation in vitro may reflect upon mechanisms of normal immunoregulation and has the potential for devising means to predict and enhance the beneficial effects of anti-Ig treatment in clinical situations.